Genetic genealogy was used to link Bryan Kohberger, suspect in Idaho slayings, to crime scene, prosecutors say

DNA on a knife sheath found at the off-campus home where four Idaho college students were killed last November directly links accused murderer Bryan Kohberger to the crime scene, according to court documents filed by prosecutors last week.

Law enforcement officials used investigative genetic genealogy to link DNA found on the sheath to Kohberger, 28, a doctoral student at nearby Washington State University studying criminology, according to the June 16 filing from the Latah County Prosecutor’s Office. The investigation found that the DNA was at least 5.37 octillion times more likely to be Kohberger's than an unrelated member of the public, the document states.

Kohberger is accused of fatally stabbing Ethan Chapin, 20, of Conway, Washington; Madison Mogen, 21, of Coeur d’Alene, Idaho; Xana Kernodle, 20, of Avondale, Arizona; and Kaylee Goncalves, 21, of Rathdrum, Idaho, on Nov. 13. A motive remains unknown.

Some information about the use of DNA to identify Kohberger was already known: Law enforcement sources previously told NBC News that DNA played a role in helping investigators hone in on Kohberger, and a probable cause affidavit unsealed in January stated that male DNA was “left on the button snap of the knife sheath” and that DNA retrieved from the trash of Kohberger’s family home in Pennsylvania on Dec. 27 showed there was a high probability it was from the biological father of the person who left the DNA on the sheath at the crime scene.

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